Apparatus and method of rapidly measuring hemispherical scattered or radiated light

A scatterometer for measuring light reflected angularly from a point comprising:

• a power controlled laser light source for illuminating the point,
• a fiber optic bundle for collecting light beams reflected from the point and having a plurality of optical fibers of unequal length the one ends of each of which are fixed in spaced relation to each other in a curved surface having a radius of curvature such that the longitudinal axis of each of the fibers at the one end substantially converges at a common light source that radiates light normal to each fiber and the other ends of each of which are arranged in an indexed array, whereby light radiating angularly from the point is received simultaneously at the one end by each fiber and is transmitted to the other end,
• a camera for converting the reflected light beams into electrical signals,
• the signal level of the collected light beams being raised above the dark current noise level of the camera by predetermined amounts to form sequential images stored in a frame grabber, and
• the frame grabber also sequentially digitizing and storing images and reconstructing therefrom a single scatter profile of light emanating from the point while simultaneously scaling out the signal level increases.

A scatterometer for measuring light reflected angularly from a point comprising:

• a power controlled laser light source for illuminating the point,
• a tapered fiber optic bundle for collecting light beams reflected from the point and having a plurality of optical fibers the one ends of each of which are fixed in spaced relation to each other in a curved surface which is a spherical segment in the tapered portion of the bundle having a radius of curvature such that the longitudinal axis of each of the fibers at the one end substantially converges at a common light source that radiates light normal to each fiber and the other ends of each of which are arranged in an indexed array, whereby light radiating angularly from the point is received simultaneously at the one end by each fiber and is transmitted to the other end,
• a camera for converting the reflected light beams into electrical signals,
• the signal level of the collected light beams being raised above the dark current noise level of the camera by predetermined amounts to form sequential images stored in a frame grabber, and
• the frame grabber also sequentially digitizing and storing images and reconstructing therefrom a single scatter profile of light emanating from the point while simultaneously scaling out the signal level increases.

A scatterometer for measuring light reflected angularly from a point comprising:

• a power controlled laser light source for illuminating the point,
• a tapered fiber optic bundle having
• a plurality of individual fiber optic elements having a common field of view which is the point for collecting light beams reflected therefrom,
• a concave face on the tapered portion at one end, and
• the other end formed as an indexed array adapted for transmitting the collected light beams,
• a CID camera having a scannable area array for receiving the transmitted light beams and for converting the reflected light beams into electrical signals,
• the signal level of the collected light beams being raised above the dark current noise level of the camera by predetermined amounts to form sequential images stored in a frame grabber, and
• the frame grabber also sequentially digitizing and storing images and reconstructing therefrom a single scatter profile of light emanating from the point while simultaneously scaling out the signal level increases.

A scatterometer for measuring light reflected angularly from a point comprising:

• a housing,
• a power controlled laser diode light source supported within the housing for illuminating the point,
• a tapered fiber optic bundle supported within the housing and having
• a plurality of individual fiber optic elements having a common field of view which is the point for collecting light beams reflected therefrom,
• a concave face on the tapered portion at one end, and
• the other end being formed as an indexed array adapted for transmitting the light beams reflected from the point,
• a CID camera supported within the housing and having a scannable area array for receiving the transmitted light beams and for converting the reflected light beams into electrical signals,
• the signal level of the collected light beams being raised above the dark current noise level of the camera by predetermined amounts to form sequential images stored in a frame grabber, and
• the frame grabber also sequentially digitizing and storing images and reconstructing therefrom a single scatter profile of light emanating from the point while simultaneously scaling out the signal level increases.

A scatterometer for measuring light reflected angularly from a point and having means for reconstructing a single data profile from data stored in a plurality of sequential x-y oriented memory frames of a computer frame grabber the first frame of which is a reference frame in which the data represents a factor common to all frames in the sequence and the remaining frames of which are data frames, comprising:

• a power controlled laser light source for illuminating the point,
• a fiber optic bundle having a plurality of individual fiber optic elements having a common field of view which is the point for collecting light beams reflected therefrom,
• a camera for converting the reflected light beams into electrical signals,
• the signal level of the collected light beams being raised above the dark current noise level of the camera by predetermined amounts to form sequential images stored in a frame grabber, and
• the frame grabber also sequentially digitizing and storing images and reconstructing therefrom a single scatter profile of light emanating from the point while simultaneously scaling out the signal level increases,
• and further comprising:
• a) means for setting an x-y oriented array in memory and filling the array with zeros,
• b) means for computing a scale factor,
• c) means for subtracting the common factor data in the reference frame from the data in each of the data frames in the sequence,
• d) means for scaling the data in the first data frame by the scale factor and adding the scaled data to the profile array,
• e) means for scaling and adding the data stored in each x-y point in the next succeeding data frame to its corresponding x-y location in the profile array only if it has not been previously stored in that location, and if
• (1) the data already in the x-y point in the profile array is zero, and
• (2) the data in that x-y point in the current and any prior data frame is less than T, where T is a threshold level representing a level above which the data is invalid, and
• f) means for repeating step (e) separately in sequence for each subsequent data frame in the sequence.

A method for measuring light reflected angularly from a point in a scatterometer comprising the steps of:

• power controlling a laser light source for illuminating the point,
• collecting the light beams reflected from the point in a fiber optic bundle having a plurality of individual fiber optic elements having a common field of view which is the point,
• converting the reflected light beams into electrical signals in a camera,
• raising the signal level of the collected light beams above the dark current noise level of the camera by predetermined amounts to form sequential images stored in a frame grabber,
• sequentially digitizing the stored images in the frame grabber, and
• reconstructing therefrom a single scatter profile of light emanating from the point while simultaneously scaling out the signal level increases.